Method of applying protective coatings



Patented Apr. 9, 1946 METHOD OF APPLYING PROTECTIVE COATINGS MartinSalo, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Application July-3, 1942,Serial No. 449,675

15 Claims. (01.117-457) This invention relates to a method of formingprotective coatings upon surfaces by applying thereto a moltencomposition of a cellulose ether and a'pla'sticizer therefor. I

Heretofore ethyl cellulose has been employed in melt coatingcompositions, but only in small quantities, in compositions in which waxor moistureproofing material predominated, 'the ethyl celluloseapparently being employed merely to impart better film-formingproperties to the compositions.

These coatings have been characterized by considerable softness atordinary temperature and they melt at comparatively low temperatures.Therefore, the field for usefulness of those coatings is quite limitedand their durability leaves much to be desired.

The prior art has taught that when ethyl cellulose was employed in anamount greater than 20% of a composition, the mass was not properlyfiowable and the moisture transmission of the composition was too great.In no case has there been any indication in the prior art that any ofthe cellulose eth'ers, particularly ethyl cellulose, have been suitablemerely mixed with plasticizer for satisfactorily melt coating materialsupon which a protective covering is desirable.

An object of my invention is to provide a process of applying protectivecoatings to surfaces, which coatings protect the surface against thewear and weathering which might be met with in the use of variousmaterials such as paper, fabric, and the like. Other objects or myinvention will appear herein.

I have found that ethyl celluloseshaving certain restricted propertieswhen mixed with an amount of plasticizer forming at least 20% of thecomposition can be applied as a melt to a surface and'will give aflexible, glossy, smooth, and transparent coating which will withstandimpact creasing without breaking. I have found that molten compositions,in accordance with my invention, can be applied to paper, glass, cloth,metal, leather, wire, or any other susceptible material, particularlyhaving a smooth surface, thereby forming a protective covering thereon.I have found that melt coatings, in which at least 50% of thecomposition is an ethyl cellulose as described herein, are firm anddurable and resistant to the effects of moderate heat and light. Themelted cellulose ether compositions described may be applied in anydesired manner which will give a smooth, thin, uniform coating on thecloth, paper, or other material to be coated. For instance the moltenmaterial may be flowed from the hopper through a restricted opening ontoa cloth, paper, or the like as the latter is moved along under thehopper. coating 9. blade, adjusted as desired, may be in the line ofmovement almost immediately after the hopper to spread the coating whileit is still in a soft condition. Instead of a blade some other spreadingmeans, as an air brush, may be used. As the coating cools and solidifiesrapidly the coated cloth, paper, or the like may be wound up in a, rollshortly after the application on the coating.-

If desired the molten mixture of the cellulose ether and plasticizer maybe applied to the cloth, paper, etc., by spraying it thereon. In thisway the application of the melt to the surface may be manuallycontrolled and is particularly useful where a surface of uneventhickness is desired.

The molten coating material may be applied by means of an applicatorroll, either .one which dips in the melted material and is heated tomaintain the coating material in a melted condition until it contactsthe cloth, paper, etc., which is to be coated, or one which is heatedand to before it has had time to harden, it is preferred that the coatedmaterial be subjected to further treatment such as by heated smoothingrolls or squeeze rolls, a blade or an air brush ifa smooth surface isdesired, or heated embossing rolls if some sort of embossing or designis wanted.

The composition which I employ essentially consists of 50-80% ethylcellulose of the type described below, mixed with at least 20% of astable compatible plasticizer. The composition may contain small amountsof wax, resin, filler or pigment, but should be substantially freeof'fiowable material. -It is desirable that this group of extramaterials make up less than 10% ofthe luloses of this typeis describedand claimed in Malm and Crane application Serial No. 410,432,

To obtain a uniform flied September 11, 1941. Stable ethyl oelluloseswill also have a high char point, ordinarily at least 300 C.

The plasticizer employed in the composition used for melt coating, inaccordance with my invention, should make up at least 20% and preferably30% of the composition. The plasticizer employed should be a stable,compatible, high molecular weight plasticizing compound. Some of theplasticizerswhich' have been found to be suitable for this purpose aredi-2-ethyl hexyl phthalate, n-butyl stearate, dibutyl sebacate, dibutylphthalate, diamyl phthalate. and glycol sebacate.

The temperature at which the coating composition is maintained ispreferably close to the melting point of the cellulose ether. As thepresence of plasticizer lowers the melting point, this temperature willordinarily just keep the composition in a melted condition. Atemperature in the range of 280-340 F. will ordinarily be found the mostuseful for ethyl cellulose compositions in accordance with my invention.According to my invention coatings having a thickness of approximately.0005 inch are ordinarily applied to surfaces. If desired, however,thicker coatings such as up to .001 inch or even more thickness may beapplied merely by speeding up the flow of the molten composition ontothe surface and by adjusting the spacing of the doctor blade or othersmoothing means to allow for greater thickness. If desired, however,coatings having much less thickness than that ordinarily employed may beused. For instance, in the coating of paper, if the paper is put throughsqueeze rolls the thickness of the resulting product may besubstantially the same as the thickness of the paper before subjectingto the coating operation.

My coating methods may be employed to coat paper, giving thereon atransparent, flexible coat ing which will protect the paper and yet willnot interfere with many and various uses. By this means a desirablewrapping material may be prepared. Also, an artificial leather may beprepared by my process by coating paper and, if desired, embossing it.For instance paper, after applying a coating thereto in accordance withmy invention, may be run through an embossing roll having a pressure of260 tons at 230 F. A highly flexible artificial leather is therebyobtained. If desired a small amount of antioxidant such as hydroquinonemight be included in the composition, particularly if the composition isto be maintained in molten condition for a considerable period of time.If desired a compatible and stable dye material may be incorporated inthe composition if a colored coating is desired. The coating which Iapply, preferably to flat or plane surfaces, is of good permanence andunder ordinary conditions will last as long as the article on which thecoated material is used. Although coating onto flat surfaces ispreferable, my coating method is adaptable to the coating of any type ofsurface, whether rough or smooth, although the coating of smoothsurfaces is more convenient and gives more uniform thickness of theprotective covering. It is, of course, desirable that coatingcompositions, in accordance with my invention, be free of any materialwhich will discolor the decomposition in use.

A satisfactory method of preparing the coating composition employed inmy process is to select an ethyl cellulose such as prepared by theprocess described in Malm and Crane application 410,432,

which ethyl cellulose has the properties described, and by ball-millingthe ethyl cellulose and then mixing it with the desired proportion ofplasticizer and any other desired ingredients, all preferably in flnelydivided form. The mixture so obtained is suitable for forming the moltencomposition for use in the protective covering of obiects in accordancewith my invention. The following examples illustrate my invention:

Example I A composition was prepared by mixing together in finelydivided form 28 parts of di-2-ethyl hexyl phthalate and '12 parts ofethyl cellulose havinl an ethoxyl content of 49%, a viscosity of 35 cps.in 10% solution in toluene-ethanol (2:1) at 25 C., melting point of 151C. and a char point of 310 C. This composition was then melted byheating to 350 F. and was coated onto paper by means of a melt coatingmachine. In this machine a measured thickness of melt was applied ontothe paper from a heated applicator roll rotating in the direction of thepaper. The melt was applied onto the applicator roll by a pick-up rollpartially submerged in the melt contained by the heated hopper androtated in a direction opposite to that of the applicator roll. Theclearance between the pick-up and applicator rolls was adjusted to givethe desired quantity of melt on the applicator roll. After the melt wasapplied onto the paperthe coating was smoothed by a heated smoothingbar. The coating hardened and became non-tacky very shortly afterleaving the doctor blade. The coating was flexible and glossy inappearance.

Example II Paper was melt coated as in Example I with a compositionconsisting of 33 parts of di-z-ethyl hexyl phthalate and 67 parts ofethyl cellulose having an ethoxyl content of 49%, viscosity of 53 cps.in 10% solution in 2:1 toluene-ethanol at 25 C., a melting point of 153C., and a char point of 310 C. A brilliant and flexible coating wasobtained.

Example III A composition consisting of 30 parts of n-butyl stearate and70 parts of the same kind of ethyl cellulose as used in the precedingexample was melt coated onto paper in the same manner. A flexiblecoating of good brilliance was obtained.

Example IV Paper was coated at 290 F. on a melt coating machine asdescribed in Example I, with a molten composition consisting of 25 partsof dibutyl sebacate and parts of ethyl cellulose having an ethoxylcontent of 47% and viscosity of 5.7 cps. in a 10% solution in 2:1toluene-ethanol, a melting point of 154 C. and a char point of 311 C. Abrilliant coating was obtained, but the flexibility was not as good aswas obtained in the previous examples, probably due to the lowerviscosity of the ethyl cellulose used.

Example V A composition consisting of 65 parts of ethyl cellulose havingan ethoxyl content of 49%, a viscosity of cps., a melting point of 169C. and a char point of 304 C. in 35 parts of 2-ethyl hexyl phthalate wasmelt coated onto paper at 340 F. in the manner described in thepreceding examples. A paper having a smooth, glossy, transparent, andflexible coating was obtained.

the paper.

What I claim anddesire to be secured by Letters Patent of the UnitedStates is:

1. A paper sheet having a flrmprotective coating thereon which isstrongly adherent at atmospheric temperatures resulting from depositingthereon in molten fully-fluid condition a thin layer of a low meltingcomposition, essentially consisting of 50-80% of a heat-stable ethylcellulose which'has an ethoxy content of 45-55% and a viscosity of -100centipoises and at least 20% of a stable, compatible, high molecularweight plasticizer.

2. Amethod of forming a protective coating upon a cellulose web whichcomprises depositing thereon in a molten fully-fluid condition alowmelting composition essentially consisting of 50-80% of a heat stableethyl cellulose having an ethoxyl content of 45-55% and a viscosity of5-100 centipoises, and at least 20% of a stable compatible highmolecular weight plasticizer so as to form a thin layer of thecomposition upon the web.

3. A method of forming a protective coating upon a paper sheet whichcomprises depositing thereon in a molten fully-fluid condition alowmelting composition essentially consisting of 50-80% of a heat stableethyl cellulose having an ethoxyl content of 45-55% and a viscosity of5-100 centipoises, and at least 20% of a stable compatible highmolecular weight plasticizer so as to form a thin layer of thecomposition upon.

4. A method of forming a. protective coating upon a paper sheet whichcomprises flowing onto that paper sheet in a molten fully-fluidcondition' a low-melting composition essentially consisting of 50-80% ofa heat stable ethyl cellulose having .an ethoxyl content of 45-55% and aviscosity of 5-100 centipoises, and at least 20% of a stablecompatible-high molecular weight plasticizer so as to form a thin layerof the compositionupon the paper. L

5. A method of forming a protective coating upon a paper sheet whichcomprises depositing thereon in a molten fully-fluidcondition alowmelting composition essentially consisting of 50-80% of a heat stableethyl cellulose having an ethoxyl content of 45-55% and a viscosity of5-100 centipoises, and at least 20% of di-2-ethy1- hexyl-phthalate so asto forma thin layer of the composition on the paper. i

6. A method of forming a protective coating upon a surface whichcomprises flowing onto that low-melting composition essentiallyconsisting of 50-80% of a heat stable ethyl cellulose having an ethoxylcontent of 45-55% and a viscosity of 5-100 centipoises and at least 20%of a stable, compatible, highmolecular weight plasticizer so as to forma thin layer of the composition upon the surface.

8. A method of forming a protective coating upon a surface whichcomprises flowing onto that surface in a molten fully-fluid condition alowan ethoxyl content of 45-55% and a viscosity of 5-100 centipoises andat least 20% of a stable,

compatible, high molecular weight plasticizer so as to form a thin layerof composition upon the surface.

9. A method of forming a protective coating upon a surface whichcomprises depositing on that surface in a molten fully-fluid condition alow-melting composition essentially consisting of 50-80% of a heatstable ethyl cellulose having an ethoxyl content of 45-55% and aviscosity of 5-100 centipoises and at least 20% of di-2-ethy1 hexylphthalate so as to form a thin layer of the composition upon thesurface,

10. A method of forming a protective coating upon a surface whichcomprises depositing on that surface in a molten fully-fluid condition alow-melting composition essentially consisting of 50-80% of a heatstable ethyl cellulose having an ethoxyl content of 45-55% and aviscosity of 5-100 centipoises and at least 20% of dibutyl sebacate soas to form a thin layer of the composition upon the surface. I

11. A cellulose web having a firm protective coating ithereonwhi'ch'isstrongly adherent at atmospheric temperaturesresulting from depositingthereon in a molten fully-fluid condition a thin layer of a low-meltingcomposition essentially consisting of 50-80% of a heat stable ethylcellulose having an ethoxyl content of 45-55% and a viscosity of 5-100centipoises and at least 20% of a stable, compatible, high molecularweight plasticizer. a

12. A cellulose web having a firm protective coating thereon which isstrongly adherent at atmospheric temperatures resulting from depositingthereon-in molten fully-fluid condition athin layer of a low-meltingcomposition essentially consisting of 50-80% of a heat stable ethylcellulose having .an ethoxyl content of 45-55% and a viscosity of 5,-centipoises and at least 20% of di-Z-ethyl hexyl phthalate.

.13. A cellulose web having a firm protectiv coating thereon which isstrongly adherent at atmospheric temperatures resulting from depositingthereon in molten fully-fluid condition a thin layer of a low-meltingcomposition essen-- tially consisting of 50-80% of a heat stable ethylcellulose having an ethoxyl content. of 45-55% and a. viscosity of5-100cejntipoises and at least 20% of dibutyl sebacate.

14. A paper sheet having a firm protective coating thereon which isstrongly adherent at atmospheric'temperatures resulting from depositingthereon in molten fully-fluid condition a thin layer of a low-meltingcomposition essentially consisting of 50-80% of a heat stable ethylcellulose which has an ethoxyl content of 45-55% and. a viscosity of5-100 centipoises and at least 20% -of di-Z-ethyl hexyl phthalate.

15. A paper sheet having a firm protective coating thereon which isstrongly adherent at atmospheric temperatures resulting from depositingthereon in molten fully-fluid condition a 'thin layer of a low-meltingcomposition essentially consisting of 50-80% of a heat stable ethylcellulose which has an ethoxyl content of 45-55% and a viscosity of5-100 centipoises and at least 20% of dibutyl sebacate.

MARTIN SALO.

melting composition essentially consisting of 50-80% of a heat stableethyl cellulose having Certificate of Correction Patent N 0. 2,398,042.April 9, 1946. MARTIN SALO It is hereby certified that error appears inthe printed specification of the above numbered patent requiringcorrection as follows: Page 1, second column, line 49, after the numeral100" insert cps. measured in a 10% solution of toluene-eth-; and thatthe said Letters Patent should be read with this correction therein thatthe same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 2d day of July, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

